On 5/14/19 9:42 AM, Dan Williams wrote:
On Mon, May 13, 2019 at 9:05 PM Aneesh Kumar K.V
<aneesh.kumar@xxxxxxxxxxxxx> wrote:
On 5/14/19 9:28 AM, Dan Williams wrote:
On Mon, May 13, 2019 at 7:56 PM Aneesh Kumar K.V
<aneesh.kumar@xxxxxxxxxxxxx> wrote:
The nfpn related change is needed to fix the kernel message
"number of pfns truncated from 2617344 to 163584"
The change makes sure the nfpns stored in the superblock is right value.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
drivers/nvdimm/pfn_devs.c | 6 +++---
drivers/nvdimm/region_devs.c | 8 ++++----
2 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 347cab166376..6751ff0296ef 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -777,8 +777,8 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
* when populating the vmemmap. This *should* be equal to
* PMD_SIZE for most architectures.
*/
- offset = ALIGN(start + reserve + 64 * npfns,
- max(nd_pfn->align, PMD_SIZE)) - start;
+ offset = ALIGN(start + reserve + sizeof(struct page) * npfns,
+ max(nd_pfn->align, PMD_SIZE)) - start;
No, I think we need to record the page-size into the superblock format
otherwise this breaks in debug builds where the struct-page size is
extended.
} else if (nd_pfn->mode == PFN_MODE_RAM)
offset = ALIGN(start + reserve, nd_pfn->align) - start;
else
@@ -790,7 +790,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
return -ENXIO;
}
- npfns = (size - offset - start_pad - end_trunc) / SZ_4K;
+ npfns = (size - offset - start_pad - end_trunc) / PAGE_SIZE;
Similar comment, if the page size is variable then the superblock
needs to explicitly account for it.
PAGE_SIZE is not really variable. What we can run into is the issue you
mentioned above. The size of struct page can change which means the
reserved space for keeping vmemmap in device may not be sufficient for
certain kernel builds.
I was planning to add another patch that fails namespace init if we
don't have enough space to keep the struct page.
Why do you suggest we need to have PAGE_SIZE as part of pfn superblock?
So that the kernel has a chance to identify cases where the superblock
it is handling was created on a system with different PAGE_SIZE
assumptions.
The reason to do that is we don't have enough space to keep struct page
backing the total number of pfns? If so, what i suggested above should
handle that.
or are you finding any other reason why we should fail a namespace init
with a different PAGE_SIZE value?
My another patch handle the details w.r.t devdax alignment for which
devdax got created with PAGE_SIZE 4K but we are now trying to load that
in a kernel with PAGE_SIZE 64k.
-aneesh
